A simple brain scan could soon transform the treatment of patients with dementia.
The scans picked up key differences in the brain
Doctors in the United States have used brain scans to distinguish between patients with Alzheimer's disease and those with vascular dementia, which is caused by poor blood flow to the brain.
Until now, both groups of patients tended to get grouped together.
This has meant that some patients may not have received the care they needed.
Neither Alzheimer's disease nor vascular dementia can be reversed.
However, treatments can help to reduce the risk of further damage in patients whose dementia has been caused by poor blood flow to the brain.
Experts at the San Francisco VA Medical Center believe the ability to distinguish between these two different types of dementia could help patients in both groups.
"Being able to determine that there is a vascular component to a patient's dementia would make a big difference in planning for treatment," said Dr Norbert Schuff.
"If we can tell the difference between people with Alzheimer's and those with vascular dementia, we can select the appropriate candidates for clinical trials of new drugs."
Dr Schuff and colleagues have based their findings on a study of 108 patients.
Of these, 43 had been diagnosed with Alzheimer's and 13 patients had suffered small strokes enabling doctors to clearly diagnose vascular dementia. The remaining 52 patients did not show any signs of dementia.
The doctors used magnetic resonance imaging (MRI) to create 3-D images of all of the patients' brains.
They used another technique, magnetic resonance spectroscopy, to look at chemical activity in key areas of the brain.
They looked particularly at levels of N-acetylaspartate (NAA). This chemical is produced when neurons, which carry electrical signals between different regions of the brain, are active.
They found that patients with vascular dementia had less NAA in the area of the brain responsible for short-term memory and decision making - the frontal cortex - compared to patients with Alzheimer's or no dementia.
They also had less NAA in the area of the brain responsible for language, known as the parietal cortex.
However, they had normal levels of NAA in the medial temporal lobe, which is responsible for memory. This compares to patients with Alzheimer's, who had reduced levels of the chemical in this area.
This chemical reading enabled doctors to identify eight out of 10 patients with vascular dementia.
When they combined the reading with results from the MRI scan they were able to identify nine out of 10 patients correctly.
The researchers said the findings suggested that patients with vascular dementia were suffering from neuronal dysfunction, which affects the ability of the neurons to communicate with each other.
This compares to patients with Alzheimer's whose neurons are no longer working.
The researchers said further studies are needed to see if their technique can identify other patients with vascular dementia.
"These patients were very carefully selected," said Dr Schuff.
"We need to see if this method for distinguishing vascular dementia from Alzheimer's can be done in a clinical setting where many other factors may contribute to dysfunction in the brain."
The study is published in the journal Neurology.